Rough surface radiant heater



July 1, 1969 L. J. REYNOLDS, JR 3,453,413

ROUGH SURFACE RADIANT HEATER I of 2 Sheet Filed Dec. 10, 1965 INVENTOR 10:11. cffiej/nolci-s, e1).

y 1, 5 L. J. REYNOLDS, JR 3,453,413

- ROUGH SURFACE RADIANT HEATER Filed Dec. 10, 1965 Sheet of 2 INVENTOR loads cf. Fey aZa J, r/z' PRIOR ART .BY I 7/1, ,j z f 16,, rLuJ/u ATTORNEY;

United States Patent U.S. Cl. 219-345 Claims ABSTRACT OF THE DISCLOSURE A relatively low temperature electric radiant panel heater has its radiating surface roughened to increase the effectiveness of the surface as a radiator. In one embodiment, sand particles are distributed over the surface and bonded thereto by an adhesive, such as an epoxy type glue. The sand particles have a substantial portion of their bulk projecting out of the surface of the adhesive, thereby increasing the effective radiation surface area of the panel. The sand particles may be decorated by use of a paint, for instance, of the styrene-butadiene base type. In an alternative embodiment, the panel surface is covered by a sheet of polyvinyl chloride having an outer surface roughened by molding in order to increase the effectiveness thereof.

This invention relates to heat transfer and more particularly to heat transfer from surfaces of a nature to emit heat primarily by radiation and at relatively low temperatures.

It has long been recognized that heat transfer by radiation is an effective means of utilizing energy in situations where the object to be heated can be seen by the heat emitter.

Effective heat emitters of the type which depend on the use of a high temperature as, for example, the sun and lamps and other electrically heated elements which attain a temperature many times that of the human body, have been known for a long time. Heaters of this nature, however, may be ineffective in certain situations, may require a large energy input, may present a hazard or may radiate such concentrated heat as to cause discomfort and hazard to a person in close proximity thereto.

The present invention contemplates providing a surface for a heat radiator of the type operating at relatively low temperatures. An example of such heating panel is disclosed in the co-pending application of Louis I. Reynolds, Ser. No. 419,283 filed Dec. 14, 1964, now Patent 3,309,500.

Heating panels of this general nature may be relatively small and placed near a person or object occupying a relatively stationary position such as at a desk or table. Such panels may also be much larger and serve an additional function as a room divider or screen which may be of the folding type. Such panels may also be mounted on the wall. In any situation it is aesthetically desirable that such panels be harmonious with the surroundings. Such harmony may be obtained by decorating the panel.

An object of the invention is to provide effective heatradiating panel and a decorative type coating therefor which coating does not unduly interfere with the radiation of heat.

A further object of the invention is the provision of an effective heat-radiating surface which operates at relatively low temperatures and has an ornamental coating which emits heat primarily by radiation and only minimally by conduction and which rapidly reaches a steady state temperature.

Other objects will be apparent from the following de- 3,453,413 Patented July 1, 1969 scription, in conjunction with the in which:

FIG. 1 is a perspective of a heating panel according to the present invention having a decorative picture painted thereon, and mounted on a wall;

FIG. 2, a section of a portion of the panel on line 2-2 of FIG. 1;

FIG. 3, a schematic illustrating the wiring of the panel of FIG. 1;

FIG. 4, a perspective of the resilient clip used in the present invention;

"FIG. 5, a perspective illustrating the application of a simulated wood grain finish to a panel according to the present invention;

FIG. 6, a cross-section of another modification of the present invention in which the heating panel is covered by a vinyl membrane having a roughened outer surface.

FIG. 7, a schematic cross-section of a heating panel according to the present invention which illustrates schematically heat transmission through a surface member constructed according to the present invention; and

FIG. 8, a cross-section similar to FIG. 4 of a surface member of cement alone covering a heating panel and indicating schematically different heat transmission characteristics of a panel which does not have structure of the present invention.

Briefly stated, the present invention includes the providing of a heat conductive relatively thin sheet member with an effective heat-radiating surface. This may be obtained by bonding to the surface a substance having effective heat radiating properties. It has been found, for example, that particles such as silica sand form an effective heat radiator. A layer of such particles is distributed over the surface and bonded to it by a suitable adhesive such as an epoxy type glue. The particles are distributed over the glue after the latter is applied to the sheet member and have a substantial portion of their bulk projecting out of the surface of the adhesive. The embedded particles may be decorated by the use of a paint such as a styrene-butadiene base paint such as one commonly known as ?Super Kem-Tone, manufactured by Sherwin-Williams Company. Such paints do not flow after they are dry or change their color, even when subjected to temperatures in excess of those used in panels of this nature for a long period of time.

Referring to the drawings, an illustrative heating panel 1 is surrounded by frame members 2 and mounted on a wall 3. The panels may be made in many sizes and shapes such as those disclosed in the earlier cited co-pending application. The panel includes an electrical heating unit 5 including an electrical power lead 6 with its two wires 7, 8 crimped to copper electrodes 9 and 10 secured respectively to opposite edges of a sheet-like electrical conductive element 12. Electrical current heats conductive element 12 to a desired temperature which is substantially uniform over its entire surface. A thermostat 14 is connected in the power lead 7 to cut off electric flow to the conductive element when a desired temperature is reached.

The electrical conductive element here illustrated is one made by Chemelex, Inc., and sold under the trade name of Cellotherm. As sold, the unit includes the electrodes 9 and 10 and two sheets 13 of asbestos which cover and electrically insulate the conductive coating. The Cellotherm heating unit and the thermostat 14 are taped to a sheet of insulation 15 by a transfer tape 16 utilizing heat resistant adhesive.

A metal protective plate 28, covered by a layer of an epoxide glue 29 in which a layer of sand or similar granular or fragmented siliceous particles 31 is embedded, is mounted over insulation sheet 15. Glass batting 20 or other accompanying drawings,

suitable insulating material covers the Cellotherm sheet on the side opposite insulatioin sheet 15 and backing board 21 is mounted on the opposite side of the glass batting. Backing strips 22 secured to the frame elements 2 engage the rear surface of backing board 21 near its edges. A number of resilient strips 9 are folded in half and inserted between the inner edges of frame member 2 and the outer edges of the backing board 21, the glass batting 20, the Cellotherm sheet 21, the insulation sheet 15, and the protective plate 28 to hold the assembly together.

Before assembling of the parts described, the protective plate 28 is covered with the layer of cement 29, the sand particles 31 are embedded therein, and after the cement dries the surface may be decorated.

An epoxide glue such as that manufactured by Emerson & Cummings, Inc. under the trade name of Eccocoat EC. 210, has been found satisfactory for cement 29. It is supplied as two components, an epoxide resin solution and a catalyst. The parts are mixed in accordance with instructions of the manufacturer and are applied to the protective plate 28 by rolling to form a coating preferably ranging in thickness from approximately 0.0020 to 0.0029 inch.

The cement is normally applied when it has viscosity of approximately 58 to 63 Kreb units at normal room temperatures. Normally the operator judges this viscosity by sight and feel only and allows the cement to set for approximately one-half hour after mixing and applies it when he feels the cement will form a layer of the desired thickness.

The coating is allowed to stand for approximately onehalf hour and sand is then uniformly sprinkled over the coating. At this time, the viscosity of the cement is such that the sand particles sink in the cement to become well embedded therein but a substantial portion of the particles projects above the cement surface. The cement forms a tight bond with the embedded sand particles and ef ficiently transmits heat to them from the protective plate 28.

The particular sand used by applicant was obtained in the desert in the vicinity of Santa Fe, N. Mex. The panticles were of a size such that 100% passed through a 40-mesh screen. Other types of sand or particles of other substances having good heat radiating properties would also be useful in this invention. Included are various silicates such as aluminum silicates.

After the cement dries, the panel is shaken while inverted or on its side and brushed to remove loose particles. The panel would be an efficient radiator of heat at this state and might be aesthetically acceptable in certain surroundings. However, the surface is usually painted thereafter either in a solid color or in a desired design. Application of a styrene-butadiene paint known as Super Kem-Tone by rollers has been satisfactory. Acrylic and casein base paints may also be satisfactory. The rough texture of the sand surface is suitable for the painting of pictures thereof. The paint, when applied, should be sufficiently thin so that the underlying rough texture is not destroyed. If the paint is too thick, the outer surface would be smooth and tend to reflect rather than radiate heat transmitted to it from the interior of the panel. Areas such as 34, FIG. 2, may be left unpainted if desired, since the underlying sand has a pleasing appearance of itself.

If desired, an ornamental wood grain appearance can be placed on the protective plate instead of a painted design by brushing or sanding the surface after the first layer of sand and cement dries and then applying additional cement in thin streaks 35 by allowing it to drip from a stick 36 dipped into the epoxide mixture. The cement is best allowed to set for several hours after mixing so its viscosity is higher than that applied in the first layer. Accordingly, it forms relatively thick streaks. The streaks are formed into patterns comparable to natural wood grain by appropriate movements of the stick over the 4 surface. While streaks of cement are still wet, additional sand is sprinkled on the surface as before.

In FIG. 6, a protective plate 28" is covered by a sheet or membrane 46 of polyvinyl chloride having a roughened outer surface 47 formed by molding. Panels having such coatings with roughened surfaces have been found acceptable in certain situations. Similar coatings and sheets may be made of various materials that can be formed with a roughened surface and will not deform within the temperature ranges (including a reasonable safety allowance) that might be reached in use.

After the cement and any paint or other ornamentation has dried, the panel is assembled. In use, the panels are mounted on the wall or otherwise located as desired and the power lead connected to a suitable source of electricity.

The effect of the surface construction of this invention in increasing the heat radiating properties of the panel and the reasons why smooth surfaces are less efficient radiators of heat than roughened surfaces can be best appreciated by reference to FIGS. 7 and -8. These contrast by schematic illustrations heat emission from a panel having said particles partially embedded in a cement bonded to the surface with the heat emission from a panel having a smooth surfaced outer metal plate Without the surface covering of this invention.

As illustrated in FIG. 7, heat waves generated by electric heating unit 5 are transmitted through electrical insulation sheet 15, the protective plate 28 and the cement layer 29, to heat the sand particles 31. A small amount of the heat is reflected back from the outer surface 33 of protective plate 28, but most of the heat passes to the cement since the latter is in contact with surface 3-3. Similarly, cement layer 29 heats the particles 31 by conduction. Particles 31, being of sand, a relatively good emitter of heat by radiation, emit heat as radiant heat waves 39 from each area portion of the surface of each particle which projects above the cement layer. Waves 39 are radiated at directions substantially perpendicular to each individual area of particle surface. The particles, having many surfaces facing in different directions, radiate heat in random directions including to occupants who are not directly in front of the panel. The relatively small amount of heat reflected from the surface of the particles back into their interior, as indicated by waves 40, are not generally reflected back toward heating element 12; they only heat the particle itself, and the heat is for the most part eventually radiated to the room. To a certain extent, the particles heat air in contact with them by conduction, and this heat is transmitted by convection, as indicated by wavy arrows 41. However, the amount of such heat transfer is relatively small.

In contrast, FIG. 8 illustrates heat transmission in a similar panel 1 with a layer of sheet metal 43 having an outer surface 44 comprising its outermost member. Heat generated in conductive element 12' passes through electrical insulation 15' to sheet metal layer 43. Any reflected waves 40' are reflected directly back toward the heat couductive element 12. More heat is transferred by conduction to the air and thereafter by convection as indicated by wavy arrows 41, than is transmitted by the panel of FIG. 7. Such radiant waves 39' as are emitted are propagated in a single direction perpendicular to surface 44' and heat only those occupants of the room directly in front of the panel. Such heat being concentrated, might feel uncomfortable to persons in close proximity thereto.

Thermostat 14 shuts off the electrical current when the temperature of the electroconductive element 12 reaches F., the desired level. Accordingly, an appropriate heat source may be automatically maintained at a relatively low temperature. Because of the operating charac teristics the panel is not at such a high temperature as to constitute a hazard to the occupant or to any ordinary flammable substance present.

It will be readily apparent that a surface construction has been provided which is especially designed to transfer heat at relatively low temperature by radiation and which may be in the form of panels, either decorated or plain. The device quickly reaches a steady state temperature at which substantially all of the heat delivered to the radiating surface areas is transmitted therefrom.

It will be obvious to one skilled in the art that various changes may be made in the invention without departing from the spirit and scope thereof, and, therefore, the invention is not limited by that which is illustrated in the drawings and described in the specification, but only as indicated in the accompanying claims.

What is claimed is:

1. A panel heater for the efiicient radiation of heat comprising relatively broad substantially flat plate means of substantially good heat conductivity, means for heating said plate means substantially uniformly, said plate means having a thin layer of cement forming an outer surface means, said outer surface means generally facing objects to be heated, a layer of sand particles having high heat radiating properties embedded on and substantially entirely covering said surface means, whereby the particles have good heat conducting relationship with said plate, substantial portions of said particles projecting above said surface means whereby heat from said plate is transmitted from said plate and said surface means to said particles and is radiated from the projecting surfaces of the particles in diverse directions towards objects to be heated.

2. The structure of claim 1 in which the cement is an epoxide.

3. The structure of claim 1, and a heat-transmitting paint applied over said embedded particles said paint being sufficiently thin as to avoid substantial leveling of the projecting portions of said particles with the spaces therebetween.

4. The structure of claim 1, in which the said particles are of a siliceous material.

5. The structure of claim 1, in which the particles are of a naturally occurring siliceous sand of a size such that passes through a 40-mesh screen.

References Cited UNITED STATES PATENTS 1,644,255 10/1927 Kercher et a1. 2,152,934 4/ 1939 Trent. 2,343,542 3/ 1944 Faunce 165-133 X 2,545,805 3/1951 Callender 219-345 2,715,668 8/1955 Booker et a1 219-345 2,922,866 1/ 1960 Hicks 219-345 X FOREIGN PATENTS 748,650 5 195 6 Great Britain.

ANTHONY BARTIS, Primary Examiner.

US. Cl. X.R. 126-92; -49, 133; 219-213, 530, 540 

